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Vika [28.1K]
3 years ago
7

2x + 7 + 6x - x what is equivalent to

Mathematics
1 answer:
Anna007 [38]3 years ago
5 0

Answer:

x=1

Step-by-step explanation:

2x+6x-x=7

7x=7

x=1

...............

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Math<br><br><br><br> pls help!!<br><br><br><br><br><br> answers?
statuscvo [17]

Answer: Choice B) Infinitely many solutions

  • one solution: x = 8, y = -7/2, z = 0
  • another solution: x = -12, y = 13/2, z = 10

=======================================================

Explanation:

Here's the starting original augmented matrix.

\left[\begin{array}{ccc|c}  1 & 0 & 2 & 8\\5 & 1 & 9 & 73/2\\-4 & 0 & -8 & -32\\\end{array}\right]

We'll multiply everything in row 3 (abbreviated R3) by the value -1/4 or -0.25, which will make that -4 in the first column turn into a 1.

We use this notation to indicate what's going on: (-1/4)*R3 \to R3

That notation says "multiply everything in R3 by -1/4, then replace the old R3 with the new corresponding values".

So we have this next step:

\left[\begin{array}{ccc|c}  1 & 0 & 2 & 8\\5 & 1 & 9 & 73/2\\1 & 0 & 2 & 8\\\end{array}\right]\begin{array}{l}  \ \\\ \\(-1/4)*R3 \to R3\\\end{array}

Notice that the new R3 is perfectly identical to R1.

So we can subtract rows R1 and R3, and replace R3 with the result of nothing but 0's

\left[\begin{array}{ccc|c}  1 & 0 & 2 & 8\\5 & 1 & 9 & 73/2\\0 & 0 & 0 & 0\\\end{array}\right]\begin{array}{l}  \ \\\ \\R3-R1 \to R3\\\end{array}

Whenever you get an entire row of 0's, it <u>always</u> means there are infinitely many solutions.

-------------------

Now let's handle the second row. That 5 needs to turn into a 0. We can multiply R1 by 5, and subtract that from R2.

So we need to compute 5*R1-R2 and have that replace R2.

\left[\begin{array}{ccc|c}  1 & 0 & 2 & 8\\0 & 1 & -1 & -7/2\\0 & 0 & 0 & 0\\\end{array}\right]\begin{array}{l}  \ \\5*R1-R2 \to R2\ \\\ \\\end{array}

Notice that in the third column of R2, we have 9-5*2 = 9-10 = -1. So we have -1 replace the 9. In the fourth column of R2, we have 73/2 - 5*8 = -7/2. So the -7/2 replaces the 73/2.

--------------------

At this point, the augmented matrix is in RREF form. RREF stands for Reduced Row Echelon Form. It seems a bit odd that the "F" of "RREF" stands for "form" even though we say "form" right after "RREF", but I digress.

Because the matrix is in RREF form, this means R1 and R2 lead to these equations:

R1 : 1x+0y+2z = 8\\ R2: 0z+1y-1z = -7/2

which simplify to

R1: x+2z = 8\\R2: y-z = -7/2

Let's get the z terms to each side like so:

x+2z = 8\\x = -2z+8\\\text{ and }\\y-z = -7/2\\y = z-7/2\\

Therefore, all of the solutions are of the form (x,y,z) = (-2z+8, z-7/2, z) where z is any real number.

If z is allowed to be any real number, then we can simply pick any number we want to replace it. We consider z to be the "free variable", in that it's free to be whatever it wants. The values of x and y will depend on what we pick for z.

So the concept of "infinitely many solutions" doesn't exactly mean we can pick just <em>any</em> triple for x,y,z (admittedly it would be nice to randomly pick any 3 numbers off the top of my head and be done right away). Instead, we can pick anything we want for z, and whatever we picked, will directly determine x and y. The x and y are locked into place so to speak.

Let's say we picked z = 0.

That would lead to...

x = -2z+8\\x = -2(0)+8\\x = 8\\\text{ and }\\y = z-7/2\\y = 0-7/2\\y = -7/2\\

So z = 0 would lead to x = 8 and y = -7/2

Rearranging the items in alphabetical order gets us:

x = 8, y = -7/2, z = 0

We have one solution of (x,y,z) = (8, -7/2, 0)

Now let's say we picked z = 10

x = -2z+8\\x = -2(10)+8\\x = -12\\\text{ and }\\y = z-7/2\\y = 10-7/2\\y = 13/2\\

So we have x = -12, y = -13/2, z = 10

Another solution is (x,y,z) = (-12, 13/2, 10)

There's nothing special about z = 0 or z = 10. You can pick any two real numbers you want for z. Just be sure to recalculate the x and y values of course.

To verify each solution, you'll need to plug them back into the original equations formed by the original augmented matrix. After simplifying, you should get the same thing on both sides.

8 0
2 years ago
Write the ordered pair for the point S.
beks73 [17]

Given:

The location of point S on a coordinate plane.

To find:

The ordered pair for the point S.

Solution:

A point is defined as (x,y), where, |x| is the distance between the point and y-axis, and |y| be the distance between the point and x-axis. Signs of coordinates depend on the quadrant.

From the given graph it is clear that,

Distance between S and y-axis = 3.5

Distance between S and x-axis = 5.5

Point S lies in 3rd quadrant, it means x- and y-coordinates are negative.

Therefore, the ordered pair of point S is (-3.5,-5.5).

8 0
2 years ago
|-3 + 15| what is the sum (answer) ? I think it is 12 but my friend thinks it is 18. Who is right?
Aliun [14]
I do believe it is 12 as well considering the fact that it's negative three and not positive. If it was a positive three then maybe it would be 18.
4 0
3 years ago
Read 2 more answers
#1- Jennifer made a box plot to summarize this data. 124, 118, 129, 139, 133, 129, 142, 135, 122, 137. What is the median, the l
svp [43]

Answer:

B or

Lower quartile: 124

Median: 131

Upper quartile: 137

Step-by-step explanation:

To find the median first make the data in order from greatest to least:

118,122,124,129,129,133,135,137,139,142

Then find the middle 2 numbers which are 129 and 133

129+133=262 (divide by 2 to find average) so

median= 262/2=131

To find the Lower quartile find the number in the middle of the first 5 numbers which is 124

To find the Upper quartile find the number in the middle of the second 5 numbers which is 137 so

B or

Lower quartile: 124

Median: 131

Upper quartile: 137

8 0
3 years ago
Humans breathe about 15 breaths in a minute. The average
NeX [460]

Answer:

Humans breathe about 300 liters of air in 25 minutes

7 0
2 years ago
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